Mark asked whether street trees have economic development benefits, on top of the obvious quality of life benefits, and Teresa pointed to a round-up by the Arbor Day Foundation; I decided to go a little further and dig up some primary sources. Copied over here for my own future reference, plus just a little bit of math based on the first source:

$50k median taxable value in Ypsilanti * 3% increase from street trees * 33.67 mills for all local property taxes = $50.51 / year tax revenue increase due to each street tree added to an Ypsilanti home that doesn't have one.